services/cdn: add how-tos for managing assets (#666)

docs/services/cdn/README.md

@@ -79,4 +79,6 @@ Among many others:
 
 :dart: Learn how to [upload assets to the CDN](how-to/upload-assets.md)
 
+:dart: Learn how to [manage CDN assets](how-to/manage-assets.md)
+
 :books: [CDN reference documentation](reference/README.md)

docs/services/cdn/how-to/.pages

@@ -0,0 +1,4 @@
+nav:
+    - upload-assets.md
+    - manage-assets.md
+    - ...

docs/services/cdn/how-to/manage-assets.md

@@ -0,0 +1,36 @@
+---
+tags: [cdn, how-to]
+---
+
+# Manage CDN assets
+
+This how-to guide shows you how to list and manage assets on the [CDN](../README.md). 
+
+In most cases you only need to upload new assets through the GitHub Action.
+In the rare case you need to manage the assets directly, you can do so through the Google Cloud Console.
+
+## Prerequisites
+
+- You have previously uploaded assets to the CDN. If not, see [Upload assets to the CDN](upload-assets.md).
+
+## Find reference to bucket
+
+Assets are stored in a Google Cloud Bucket.
+To find the bucket name:
+
+1. Open the [NAIS console](https://console.<<tenant()>>.cloud.nais.io) in your browser.
+2. Select your team.
+3. Select the **Settings** tab.
+4. Under the **Managed resources** section, look for the heading named **Team CDN bucket**.
+5. Click the link (`nais-cdn-<<tenant()>>-<team>-<hash>`) to view the bucket in Google Cloud Console.
+
+## List and manage assets through Google Cloud Console
+
+The bucket view in Google Cloud Console lists your team's uploaded assets.
+This might be useful to verify that your uploaded assets are present, or to delete assets are no longer needed or were erroneously uploaded.
+
+Some other common tasks you can perform in the Google Cloud Console:
+
+- [View and edit object metadata](https://cloud.google.com/storage/docs/viewing-editing-metadata)
+    - [Set Cache-Control headers](https://cloud.google.com/storage/docs/caching) (though this will be overwritten by the GitHub Action on the next upload)
+- [Delete objects](https://cloud.google.com/storage/docs/deleting-objects)

docs/services/cdn/how-to/upload-assets.md

@@ -90,3 +90,7 @@ https://cdn.<<tenant()>>.cloud.nais.io/<team>/<destination>
 
 CORS is automatically configured to accept `GET` from any
 origin (*).
+
+## Related pages
+
+:dart: Learn how to [manage CDN assets](manage-assets.md)